This invention relates generally to x-ray source measurement methods and apparatus, and more particularly to methods and apparatus for measuring a focal spot profile of an X-ray source.
The X-ray source focal spot is an important physical parameter of a CT imaging system, x-ray imaging system, mammography system, radiation therapy system, or x-ray inspection system that influences the image resolution, slice sensitivity profile, dose profile, and many other image quality characteristics. The X-ray source is regularly replaced in imaging systems installed in a clinical setting, thus, it would be useful to measure the focal spot size and shape when the X-ray source is installed on the imaging system.
Additionally, the size and shape of the focal spot can vary over time, and changes in the focal spot size can be an indication of imminent tube failure. The ability to measure the focal spot size directly on the imaging system could therefore be used as a predictor of tube failure, enabling maintenance to be scheduled to minimize customer impact.
Additionally, X-ray sources may eventually have the capability to adjust their focal spot sizes in order to improve image quality or X-ray source reliability. However, to take advantage of this capability, focal spot size must be measured directly on the imaging system, without any additional equipment.
At least some methods for measuring focal spot size and shape are known, such as the pin-hole method (point spread function) or the slit method (line spread function). However, these methods require additional hardware (such as a pin-hole or a slit) not generally available on imaging systems.